Insulating material

ABSTRACT

A method of providing insulation between joists 31, 32 during building comprises unrolling a batt of mineral fibre which has, at least at its longitudinal edges, top 35, 45 and bottom 33, 43 layers. The bottom layer 33, 43 can be compressed to fit between joists, whilst the top layer 35, 45 extends across the joists, which adjacent strips 35, 45 abutting one another, to minimize cold bridging. The batt can be formed of two layers 33 and 35, 43 and 45 which may be manufactured by slitting a single web into two layers followed by winding the two layers together to form a roll.

The present invention relates to insulation formed of mineral woolprovided in roll form and its use to insulate spaces between paralleljoists and which minimises cold bridging effects.

It is well known to provide insulation formed of mineral fibre wools,for instance glass wool and rock wool, in roll form. It is known toprovide the roll such that the batt of mineral wool is of a suitablewidth for fitting between joists, for instance ceiling joists in lofts,positioned at standard distances for instance 400 mm centres or 600 mmcentres. One product which has been available for some time comprises a100 m thick and 570 mm wide material wound into a roll. This providedadequate insulation to meet minimum requirements in the past. Buildingregulations have been increasing the requirements for minimum insulationand calculations of the insulation performance or "U values" must takeinto account the effect of thermal bridging at mortar joints, timberjoists and studwork. This has meant that thermal bridging at ceilingjoists should be minimised.

One way of improving the U values is to use thicker insulation betweenthe joists, for instance 150 or 180 mm. However with the standard widthroll the, even where the joists are of a lesser depth than the thicknessof the insulation, cannot prevent thermal bridging. A roll formed of 150mm thick homogenous batt can be adequately pushed between the joists tofill the gap, but the upper portion, extending above the joists cannotoverlap the joists adequately to provide insulation above the joist.

Whilst increasing the thickness of a standard rectangular section battto around 180 mm would provide adequate U values, single thickness ofloft insulation greater than the height of the joist results in theinsulation being compressed in thickness when it is installed underbracing timbers which are typically nailed across the tops of theceiling joists to aid roof stability.

One solution to this problem is the Rockwool EnergySaver Super 150 mmloft insulation. This consists of a double layer of mineral wool woundin a single roll. The bottom layer is 100 mm thick, whilst the top layeris 50 mm thick. The roll is unwound in the normal manner so that thebottom 100 mm layer fits in the gap between joists. The top 50 mm layeris subsequently loosened and re-positioned by moving it sideways so thatit overlies a joist. Top layers of adjacent strips are positioned sothat their longitudinal edges abut one another. Since the roll isnarrower than the distance between the joist centres (in order that thebottom layer fits between the joists) at least one additional strip ofthe top layer is required to cover the entire area over the joists. Thetwo step laying procedure is, in addition, time consuming.

Another way of overcoming the problem of thermal bridging is disclosedin U.S. Pat. No. 4,303,713. The insulating material is again provided astwo components. A first relatively wide length of insulating materialhas elongated slits and notches which act as scores to allow the stripto be folded into a U-shaped configuration so as to line the gap betweenjoists. The top arms of the U can be folded over to form flanges on eachside which overlie the joists and, optionally, overlap with thecorresponding flange on the strip positioned in the adjacent spacebetween joists. Into the U-shaped cavity is unrolled a second insulatinglayer. This solution is even more complex than the preceding one as itrequires separate positioning of two different types of material andfurthermore the provision of slits and notches increases themanufacturing complexity.

Another solution is disclosed in CA-A-1091886. A roll of material has asubstantially T-shaped cross-section such hat the base part of the Tsits between the joists, whilst the top flange sections extend over thetop of the joists. The T-shaped batt can be made either by cuttingnotches along the longitudinal edges of a rectangular section batt, ormay be made by lying a wider strip centrally on top of a narrower strip.Both methods of manufacture are relatively complex. In addition, whenthe batt is wound in a roll, the ends are not smooth and can becomedamaged, thereby damaging the flange sections which may reduce theinsulation properties.

Flex-A-Batt is an insulation roll product made by Rockwool Limited andRockwool International A/S which has improved flexibility such that whensqueezed widthways, it retains some elasticity, exerting outwardlydirected pressure, for instance on joists between which the batt ispushed. This allows a roll of material having a width equal to thedistance between joist centres (400 mm or 600 mm, for instance) to beused to insulate between joists whereby improved properties of fillingthe gap and consequently of insulating performance are achieved.

The present invention provides a product which is simple to manufacture,which is quick and straightforward to lay and which provides highinsulation performance by minimising thermal bridging at joists.

In a new method of providing insulation between sets of parallel joistshaving centre lines spaced X mm apart and having a height Y mm (having agap of depth Y mm between them), a roll of mineral fibre wool which,when unwound and relaxed forms an elongated batt with substantiallyrectangular cross-section having width X to X+40 mm and a thickness ofat least Y+50 mm and, along each longitudinal edge, comprises a toplayer and a bottom layer defined by a split from the longitudinal edgeto at least 15 mm inboard from the edge, the bottom layer being Y+25 mmthick and the top layer being at least 25 mm thick, is unwound such thatthe batt lies parallel to the joists and generally centred along themidway between a pair of joists and with the said bottom layer facingthe joists, the bottom layer is then compressed widthwise towards thebatt centreline to push the bottom layer into the space between thejoists and the top layer lies across the tops of the joists on each sideof the batt such that the top layers of adjacent batts abut each otheralong a line generally level with the joist centrelines (ie in a planepassing through the joist centreline perpendicular to the plane of thebatt).

The provision of the split between top and bottom layers in theinsulating batt allows the bottom layer to be widthwise compressibleindependently of the top layer. This allows the bottom layer to besqueezed so as to fit between the joists, whilst the top layer is notcompressed so that it is not forced into the gap between joists. Thesplit between top and bottom layers must reach to at least 15 mm inboard of the longitudinal edge. The minimum width of the split depends,to an extent, on the difference between the thickness of the bottomlayer and the height of the joists, as well as the difference betweenthe relaxed width of the batt and the distance between joistcentrelines, as well as the width of the joists themselves. The splithas its smallest minimum when the thickness of the bottom layer isapproximately equal to Y, the width of the batt is approximately equalto X and the joists are relatively narrow.

The split can be provided by forming a single cut, for instance,generally parallel to the plane of the batt, along the longitudinaledges of a generally rectangular batt, before forming it into a roll.Alternatively, but less preferably, a notch or slot can be cut into theside. Alternatively, and preferably, top and bottom layers are entirelyseparate layers. These may be provided during manufacture either byaligning two batts of equal width and rolling them together.Alternatively a single batt can be slit during manufacture andimmediately rolled.

The bottom layer generally has a thickness as close to the height of thejoist as possible. Preferably within 10 mm of the joist height.Currently in new build houses in the UK, there are two standard heights,75 mm and 100 mm. Consequently, the bottom layer preferably has athickness of 50-125 mm, more preferably 65-110 mm, for instance about 75mm or about 100 mm.

The top layer should have a minimum thickness such that when top layersof adjacent batts abutting one another overlie a joist, the thicknessacross the joist is adequate to minimise thermal bridging. A suitableminimum thickness is 25 mm, whilst the top layer is preferably at least50 mm thick. The total thickness of the batt should generally be atleast 100 mm, more preferably at least 120 mm, most preferably at least135 mm thick. It is preferable for the total thickness to be less than175 mm, most preferably less than 160 mm.

The width of the batt must be at least X, X being the distance betweenjoist centre lines. This allows top layers of batts between adjacentgaps to abut one another without the top layer having to be translated(ie moved sideways) from its original position. The total width isgenerally no more than 30 mm greater than X, preferably no more than 20mm greater than X, and preferably less than 10 mm greater than X.

The mineral wool may be glass wool or, more preferably, rock wool. Thedensity should preferably be in the range 10 to 30 kg/m³, morepreferably in the range 19 to 27 kg/m . The wool preferably is flexibleand resilient, so that it can be squeezed widthwise and retainelasticity so that it presses against the joists between which it ispushed.

The invention is illustrated further in the accompanying drawings inwhich:

FIG. 1 is a section through a pair of joists showing the problem withprovision of a uniform thick batt of mineral wool;

FIG. 2 is a section through a pair of joists showing the positioning ofEnergySaver Super 150 mm loft insulation;

FIG. 3 shows a section through two joists provided with insulationaccording to one embodiment of the present invention;

FIG. 4 represents a section through a pair of joists showing theprovision of insulation according to a second embodiment of theinvention; and

FIG. 5 is a perspective view showing the unrolling of a batt accordingto the first embodiment of the invention.

FIG. 1 shows the problem with one aspect of the prior art. A pair ofjoists 1, 2 having a height Y mm and a distance X between the centrelines are provided with a batt of insulation 3 which is, before beingpositioned between the joists, of substantially rectangular sectionhaving a width approximately X mm (for instance 400 or 600 mm), and athickness of, in this case, 150 mm. The batt fills the gap 4 between thejoists 1 and 2 but the top region 5 of the batt is compressed inwards at6 so as to leave an air gap above the joist 2. Air gaps above oradjacent to the joists are not good practice as they result in crossventilation between eaves thus reducing the insulation value. Thethickness of the insulation along the abutting line 8 above the joist 1is insufficiently thick and leads to thermal bridging.

FIG. 2 shows the solution to the problem provided in the prior art byEnergySaver Super 150 mm loft insulation. The gap between joists 11 and12, having height Y mm, is filled with a bottom layer of insulation 13,having a thickness of about Y mm. The relaxed width of the layer 13 issomewhat less than X mm, but more than the distance separating facingsides of joists 11 and 12. The layer 13 adequately fills the gap 14between joists 11 and 12. The batt 13 is provided as one layer of adouble layer from a single roll, the upper layer being a batt 15 of thesame material having the same relaxed width as the batt 13. The duallayer is provided by slitting a single, rectangular section battparallel to the plane of the batt before winding it into the roll. Thetop layer 15 is unwound with batt 13 but is subsequently loosened andmoved sideways so that it overlies joist 11. The total thickness ofinsulating material above the joist 11 at 18 is relatively high so thatthere is minimal thermal bridging. However as can be seen, in theadjacent gap between joists, 24, a batt of insulating material 23 ispositioned, whilst the associated top layer 25 is again moved (to theleft in the drawing) to overlie joist 12. This top batt 25 is positionedeven further to the left relative to associated bottom layer 23 sincethe relaxed width of the batts 15 and 25 is less than the distance Xbetween joists. consequently at least one extra strip of top layer mustbe provided to complete the insulation. In addition the two-step fittingprocedure, in which the top layers 15 and 25 have to be repositionedafter bottom batts 13 and 23 have been pushed between the joists, istime consuming.

FIG. 3 shows one embodiment of the present invention and its use toinsulate between joists 31, 32. The joists have a distance X betweentheir centres lines, in this case 600 mm. The joists are Y mm deep, inthis case 75 or 100 mm deep. The batt of insulation consists of a bottomlayer 33 and a top layer 35 which, when relaxed, have the same width,namely 600 mm. Both top and bottom layers have a thickness of about 75mm. Other thickness and combinations of thicknesses can be used. Forinstance where the joists are 100 mm high, the top layer 35 may have athickness of about 50 mm and the bottom layer 33 may have a thickness ofabout 100 m. The density of both layers is the same and is in the range19 to 27 kg/m³.

The two layers are wound together onto a roll and are positioned byunrolling along the gap between joists 31, 32. The bottom layer 33 iscompressed inwardly to fit in the space 34 between the joists. Themineral wool is sufficiently resilient that the longitudinal edges ofthe bottom layer, 39, push against the joists 31 and 32. The top layer,35, is not pushed between the joists. Since the relaxed width of thebatt is about the same as the distance between the joist centre lines,the edge 36 of the top layer 35 overlies joist 32 up to approximatelyits centre line. The longitudinal edge 36 abuts the edge 46 of top layer45 associated with bottom layer 43 of an adjacent batt 45 positionedbetween joist 32 and the adjacent joist (not shown). As can be seen, thetotal thickness of insulation above the joist along abutting edges 36and 46 of top layers 35 and 45 is the thickness of the top layer itself,in this case 75 mm.

In this first embodiment, the slit, 40 between the bottom layer 33 andtop layer 35 of the insulating batt extends across the entire area ofthe batt. In this embodiment, since the thickness of the bottom layer isabout equal to the height of the joist 31, there is no air-gap or aminimal air-gap 47 at the corner of the joist thus minimising crossventilation. Further since the total thickness of insulation above thejoist at 48 is relatively high, thermal bridging is minimised.

In an alternative embodiment of the invention shown in FIG. 4,insulating material 50 is provided between joists 51 and 52 having X mmcentres and a height of Y mm (X and Y being, in this case, 600 m and 100mm respectively). The insulating batt 50, along its longitudinal edges,consists of a bottom layer 53 and a top layer 55 having between them aslit 60 formed by cutting the material parallel to the major face of thebatt from the edge to a distance about 50 mm inboard from the edge. Thisslit allows the bottom layer 53 to be compressed inwards to fit betweenjoists 51 and 52 without causing the top layer 55 to be pulled inwards.Top layer 55 abuts top layer 65 of adjacent batt having bottom layer 63,so that the total thickness above the joist 51, shown at 58, isadequately thick to provide minimum thermal bridging. In thisembodiment, the bottom layer 53 is about equal in thickness to theheight of the joists 51 and 52. Consequently there is no air-gap orminimal air-gap 57 above the joist 51. Furthermore, the thickness at 58is greater than at 8 shown in FIG. 1, illustrating the problem solved bythe invention, even though the total thickness of insulation in thisembodiment of the invention is lower. Thermal bridging is consequentlylower in the invention than in the prior art.

FIG. 5 shows how the insulating material of the first embodiment isplaced in position. A roll 30 of rock wool batt consists of two layers33 and 35 wound together onto the roll. This dual layer product is forinstance made by splitting a single layer into two before winding it toform a roll. The single layer may be made by the process described inDE-A-3703622 whereby the flexibility of the batt is controlled bypartial crushing of the binder. The roll may be substantially as usedfor EnergySaver Super 150 mm loft insulation.

As the roll is unwound, bottom 33 provided on the outside of the roll,is positioned between joists 31 and 32, being squeezed to fill the gap34 between the joists. Top layer 35, co-wound with bottom layer 33 lieson top of bottom layer 33 and, being the same width as the distancebetween joist centrelines, extends on each side to approximately thejoist centreline. In FIG. 5, insulation 43, 45 has already beenpositioned between the joist 32 and adjacent joist (not shown). Theinsulation consists of top layer 45 and bottom layer 43 which has beensqueezed between the joists. Top layers 35 and 45 meet at 48 which islevel with the joist centrelines (that is vertically above joistcentreline).

What is claimed is:
 1. A method of providing insulation between sets ofparallel joists (31, 32, 51, 52) having a center line spaced X mm apartand being Y mm high, where X is about 400 or about 600 and Y is in therange of 75 to 100, comprising providing a roll (30) of mineral fibrewool which, when unwound and relaxed, forms an elongated batt withrectangular cross-section having width in the range X to X+40 mm and athickness of at least Y+50 mm, and which along each longitudinal edgecomprises top layer (35, 55) and a bottom layer (33, 53) defined by asplit (40, 60) which extends between the top and bottom layers from thesaid edge to at least 15 mm in board of the edge, the bottom layer beingin the range Y±25 mm thick and the top layer being at least 25 mm thickand the top and bottom layers having the same width which is in therange X to X+40 mm and having the same density unwinding the roll suchthat the batt lies parallel to the joist centered generally along theline midway between a pair of joists, and with the said bottom layerfacing the joists, andcompressing the bottom layer inwards toward thecenterline to fit the bottom layer between the joists whilst the toplayer is not compressed and lies on top of each of the pair of joistssuch that the top layers of adjacent batts abut each other generallylevel with the joist centrelines.
 2. A method according to claim 1 inwhich the split (40) extends across the entire width of the batt.
 3. Amethod according to claim 1 in which the bottom layer is in the rangeY±10 mm thick.
 4. A method according to claim 1 in which the width ofthe batt is in the range X to X+10 mm.
 5. A method according to claim 1in which the total thickness of the batt is in the range 125 to 175 mm.6. A method according to claim 1 in which X is about 400 mm or about 600mm and Y is in the range 75-100 mm.
 7. A method according to claim 1 inwhich the top layer is at least 50 mm thick.
 8. A method according toclaim 1 in which the bottom layer is about 75 mm or about 100 mm thick.9. A method according to claim 1 in which the mineral wool consists ofrock wool having a density in the range 19 to 27 kg/m³.
 10. A methodaccording to claim 1 in which the top layer is about 50 mm thick.
 11. Amethod according to claim 1 in which the top layer is about 75 mm thick.12. A method according to claim 1 in which the split between top andbottom layers extends at least 20 mm inboard of the said longitudinaledge.
 13. A method according to claim 12 in which the split between thetop and bottom layers extends at least 50 mm in board of saidlongitudinal edge.
 14. A method according to claim 13 in which the splitextends across the entire width of the batt.
 15. A method according toclaim 14 in which the top layer is about 50 mm thick.
 16. A methodaccording to claim 14 in which the top layer is about 75 mm thick.
 17. Amethod according to claim 12 in which the split between the top andbottom layers extends at least 30 mm in board of said longitudinal edgeand in which the total thickness of the batt is in the range 140-160 mm.18. A method according to claim 17 in which the split extends across theentire width of the batt.